This calculator outputs the how fast the Mazda Miata MX5 can go in each gear as calculated by the gear ratios, engine redline and tire size.
The ultimate top speed may be limted by the power, drag and aerodynamics of each individual car.

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Tire Size(345/30/20)

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OR

Tire Diameter(inches)

Final Drive Ratio

Redline (RPM)

1st Gear

2nd Gear

3rd Gear

4th Gear

5th Gear

6th Gear

7th Gear

8th Gear

RPM

1st Gear

2nd Gear

3rd Gear

4th Gear

5th Gear

6th Gear

7th Gear

8th Gear

500

2.97

4.94

7.01

0.93

11.45

0

0

0

600

3.57

5.92

8.41

1.12

13.74

0

0

0

700

4.16

6.91

9.81

1.3

16.03

0

0

0

800

4.75

7.9

11.21

1.49

18.32

0

0

0

900

5.35

8.88

12.61

1.68

20.61

0

0

0

1000

5.94

9.87

14.01

1.86

22.9

0

0

0

1100

6.54

10.86

15.41

2.05

25.19

0

0

0

1200

7.13

11.85

16.82

2.24

27.48

0

0

0

1300

7.73

12.83

18.22

2.42

29.76

0

0

0

1400

8.32

13.82

19.62

2.61

32.05

0

0

0

1500

8.91

14.81

21.02

2.8

34.34

0

0

0

1600

9.51

15.79

22.42

2.98

36.63

0

0

0

1700

10.1

16.78

23.82

3.17

38.92

0

0

0

1800

10.7

17.77

25.22

3.35

41.21

0

0

0

1900

11.29

18.76

26.62

3.54

43.5

0

0

0

2000

11.89

19.74

28.03

3.73

45.79

0

0

0

2100

12.48

20.73

29.43

3.91

48.08

0

0

0

2200

13.07

21.72

30.83

4.1

50.37

0

0

0

2300

13.67

22.7

32.23

4.29

52.66

0

0

0

2400

14.26

23.69

33.63

4.47

54.95

0

0

0

2500

14.86

24.68

35.03

4.66

57.24

0

0

0

2600

15.45

25.67

36.43

4.85

59.53

0

0

0

2700

16.05

26.65

37.84

5.03

61.82

0

0

0

2800

16.64

27.64

39.24

5.22

64.11

0

0

0

2900

17.23

28.63

40.64

5.4

66.4

0

0

0

3000

17.83

29.61

42.04

5.59

68.69

0

0

0

3100

18.42

30.6

43.44

5.78

70.98

0

0

0

3200

19.02

31.59

44.84

5.96

73.27

0

0

0

3300

19.61

32.58

46.24

6.15

75.56

0

0

0

3400

20.21

33.56

47.64

6.34

77.85

0

0

0

3500

20.8

34.55

49.05

6.52

80.14

0

0

0

3600

21.39

35.54

50.45

6.71

82.43

0

0

0

3700

21.99

36.52

51.85

6.9

84.71

0

0

0

3800

22.58

37.51

53.25

7.08

87

0

0

0

3900

23.18

38.5

54.65

7.27

89.29

0

0

0

4000

23.77

39.49

56.05

7.45

91.58

0

0

0

4100

24.37

40.47

57.45

7.64

93.87

0

0

0

4200

24.96

41.46

58.85

7.83

96.16

0

0

0

4300

25.55

42.45

60.26

8.01

98.45

0

0

0

4400

26.15

43.43

61.66

8.2

100.74

0

0

0

4500

26.74

44.42

63.06

8.39

103.03

0

0

0

4600

27.34

45.41

64.46

8.57

105.32

0

0

0

4700

27.93

46.4

65.86

8.76

107.61

0

0

0

4800

28.53

47.38

67.26

8.95

109.9

0

0

0

4900

29.12

48.37

68.66

9.13

112.19

0

0

0

5000

29.72

49.36

70.06

9.32

114.48

0

0

0

5100

30.31

50.34

71.47

9.51

116.77

0

0

0

5200

30.9

51.33

72.87

9.69

119.06

0

0

0

5300

31.5

52.32

74.27

9.88

121.35

0

0

0

5400

32.09

53.31

75.67

10.06

123.64

0

0

0

5500

32.69

54.29

77.07

10.25

125.93

0

0

0

5600

33.28

55.28

78.47

10.44

128.22

0

0

0

5700

33.88

56.27

79.87

10.62

130.51

0

0

0

5800

34.47

57.25

81.28

10.81

132.8

0

0

0

5900

35.06

58.24

82.68

11

135.09

0

0

0

6000

35.66

59.23

84.08

11.18

137.38

0

0

0

6100

36.25

60.22

85.48

11.37

139.67

0

0

0

6200

36.85

61.2

86.88

11.56

141.95

0

0

0

6300

37.44

62.19

88.28

11.74

144.24

0

0

0

6400

38.04

63.18

89.68

11.93

146.53

0

0

0

6500

38.63

64.16

91.08

12.11

148.82

0

0

0

6600

39.22

65.15

92.49

12.3

151.11

0

0

0

6700

39.82

66.14

93.89

12.49

153.4

0

0

0

6800

40.41

67.13

95.29

12.67

155.69

0

0

0

6900

41.01

68.11

96.69

12.86

157.98

0

0

0

7000

41.6

69.1

98.09

13.05

160.27

0

0

0

7100

42.2

70.09

99.49

13.23

162.56

0

0

0

7200

42.79

71.07

100.89

13.42

164.85

0

0

0

RPM

1st Gear

2nd Gear

3rd Gear

4th Gear

5th Gear

6th Gear

7th Gear

8th Gear

Some additional information on how these are calculated:

When D is the diameter of the tire, the car moves forward a distance πD with each revolution of the tire. If there are F revolutions per unit of time, it moves forward at a speed of πD´F per unit of time. If D is in inches and F is in revolutions per minute (rpm), the above result will be in inches per minute. There are 63,360 inches in a mile and 60 minutes in an hour, so one inch per minute equals 60/63360 miles per hour or 1/1056 mph. So we have the following formula:

V(mph) = D(in) ´ F(rpm) ´ (π/1056)

In the automotive industry, the coefficient 1056/π is usually taken to be equal to 336 (exactly it is 336.1352398...) and the formula corresponding to the above is:

(mph)(gear ratio)(336) = (tire diameter in inches)(rpm)

With the above numerical approximation, both formulas are identical if we consider that (rpm)/(gear ratio) is the rate of rotation of the tires. So the "gear ratio" as the number of rotations of the driveshaft for each turn of the tire. This ratio is normally more than 1, except in overdrive gear. So, calling R the "gear ratio", your final answer is:

V(mph) = D(in) ´ F(rpm) ´ (π/1056) / R

or, approximately: V = (D ´ F) / (336 ´ R)

where V is the velocity (in mph), D the tire diameter (in inches), F the engine rpm, and R the gear ratio.